At a software support center, three specialists answer phones to help solve customers problems. Calls arrive randomly (following a poisson distribution) at an average rate of 60/day. The amount of time that a specialist spends with a caller is exponentially distributed with an average of 40 min. If all specialists are busy, the callers are put on hold and they are assigned in the order of their arrival.

a) Determine the fraction of time each specialist is busy.

b) On the average, how long is a caller put on hold?

c) On the average how many callers are on hold?

d) How much time, on the average, does a caller spend on the phone?

e) What is the probability that all the specialists are busy yet no caller is on hold?